• The quantity is known as the
ATP mass action ratio. The concentration of cytochrome c
oxidase which is the terminal electron carrier in the electron
transport chain depends on the intramitochondrial ratio of
and. During rest the ATP mass
action ratio is high as the rate of ATP hydrolysis to yield ADP and
Pi is low. Hence, the concentration of reduced cytochrome c
is low thus lowering the rate of oxidative phosphorylation. But,
the increase in activity results in rapid hydrolysis of ATP to
yield ADP and Pi, thus decreasing the ATP mass action ratio. As a
result the concentration of reduced cytochrome c increases,
thereby increasing the rate of electron transport and ADP
phosphorylation.

• The mitochondrial IF1 protein regulates the enzyme
ATP synthase. In actively respiring mitochondria the pH is high.
So, IF1 is present as an inactive tetramer. But when the
pH drops below 6.5, this protein dissociates into dimers and
inhibits the activity of ATPase. These dimers bind to the interface
between the αDP and the βDP subunits thus
trapping the ATP bound to the βDP. This prevents the
hydrolysis of ATP when there is deficiency of.